SOLUTION: A certain molecule contains three as many atoms of hydrogen as oxygen and four more atoms of carbon than hydrogen. If there are 18 atoms all together in the molecule how many atom

Let "x" be the number of atoms of oxygen.
Then the number of atoms of hydrogen is 3x,
and the number of atoms of carbon is 3x+4.


Collecting altogether, we obtain


H  + O +   C    = 18
3x + x + (3x+4) = 18  ====>


7x + 4 = 18  ====>  7x = 18-4 = 14  ====>  x =  = 2.


Then the answer is:  H   O   C
                      6   2   10.

The chemical formula .

                     Naphthoquinone    ( From Wikipedia  https://www.algebra.com/tutors/faq.mpl )